Visual discrimination of simple geometrical patterns: I. Measurements for multiple element stimuli

We describe a method for the measurement of visual discrimination between simple patterns. The target to be discriminated is embedded in a background consisting of multiple, randomly positioned but identical elements, and is distinguished by a single parameter such as magnification or relative rotation. The positions of the target and background elements are varied randomly between presentations and discrimination for different values of the target parameter is measured in terms of the time taken for detection of the target. Using this method, we have studied discrimination of rotation and of magnification for simple pattern elements such as lines, triangles and squares. The results for rotation discrimination are interpreted as evidence for the activity of two discrimination mechanisms, one sensitive to the orientation of the lines from which the pattern elements are constructed and the other to the orientation of the pattern element relative to the visual field.     

The effects of retinal image motion in a simple pattern recognition task

Summary The recognition of misalignment in a pair of lines positioned end-to-end, as when setting a vernier scale, presents a simple problem in the detection of self-congruence. The accuracy with which this task can be performed has been measured both in normal vision and in the absence of retinal image motion; it is found that in the latter case the precision of the setting is decreased when the gap between the ends of the lines is small, but that the reduction in accuracy is not significant when the separation of the lines is increased to 30 min. arc. A search has been made for eye movements generating patterns of scanning activity designed to test the self-congruence of the vernier lines but without success, the distribution of spontaneous eye movements appears to be a function of the subject and not of the target lie is viewing.The reduction of vernier acuity in stabilized vision indicates that when retinal image motion is absent, the resultant pattern of neural activity is less well defined, this is ascribed to the loss of dynamic lateral inhibition effects but the reduction which occurs as the gap between the lines increases can be attributed to random neural events becoming confused with the stimulus; this hypothesis has been tested by the introduction of visual noise which is also found to reduce acuity.Now at California Institute of Technology, Pasadena, California, U.S.A.Now a guest worker at National Physical Laboratory, Teddington, England.     

Human immunodeficiency virus-specific responses in adult Ugandans: patterns of cross-clade recognition

Human immunodeficiency virus (HIV) or AIDS is currently the leading cause of death in Uganda, with at least three HIV clades (subtypes) accounting for most new infections. Whether an effective vaccine formulated on viruses from a single clade will be able to protect against infection from other local clades remains unresolved. We examined the T-cell immune responses from a cohort of HIV-seropositive individuals in Uganda with predominantly clade A and D infections. Surprisingly, we observed similar frequencies of cross-clade T-cell responses to the gag, env, and nef regions. Our data suggest that the level of viral sequence variability between distinct HIV strains does not predict the degree of cross-clade responses. High sequence homologies were also observed between consensus peptides and sequences from viral isolates, supporting the use of consensus amino acid sequences to identify immunogenic regions in studies of large populations.     

Dissociation of immune responses from pathogen colonization supports pattern recognition in C. elegans

Caenorhabditis elegans has been used for over a decade to characterize signaling cascades controlling innate immune responses. However, what initiates these responses in the worm has remained elusive. To gain a better understanding of the initiating events we delineated genome-wide immune responses to the bacterial pathogen Pseudomonas aeruginosa in worms heavily-colonized by the pathogen versus worms visibly not colonized. We found that infection responses in both groups were identical, suggesting that immune responses were not correlated with colonization and its associated damage. Quantitative RT-PCR measurements further showed that pathogen secreted factors were not able to induce an immune response, but exposure to a non-pathogenic Pseudomonas species was. These findings raise the possibility that the C.elegans immune response is initiated by recognition of microbe-associated molecular patterns. In the absence of orthologs of known pattern recognition receptors, C. elegans may rely on novel mechanisms, thus holding the potential to advance our understanding of evolutionarily conserved strategies for pathogen recognition.     

MartiTracks: a geometrical approach for identifying geographical patterns of distribution

Panbiogeography represents an evolutionary approach to biogeography, using rational cost-efficient methods to reduce initial complexity to locality data, and depict general distribution patterns. However, few quantitative, and automated panbiogeographic methods exist. In this study, we propose a new algorithm, within a quantitative, geometrical framework, to perform panbiogeographical analyses as an alternative to more traditional methods. The algorithm first calculates a minimum spanning tree, an individual track for each species in a panbiogeographic context. Then the spatial congruence among segments of the minimum spanning trees is calculated using five congruence parameters, producing a general distribution pattern. In addition, the algorithm removes the ambiguity, and subjectivity often present in a manual panbiogeographic analysis. Results from two empirical examples using 61 species of the genus Bomarea (2340 records), and 1031 genera of both plants and animals (100118 records) distributed across the Northern Andes, demonstrated that a geometrical approach to panbiogeography is a feasible quantitative method to determine general distribution patterns for taxa, reducing complexity, and the time needed for managing large data sets.     

Visual discrimination: Seeing the third quality of light.

Objects can differ in brightness and colour. At least that is what our own visual system tells us. It now seems that stomatopod shrimps, and possibly also cephalopod molluscs, can see the direction of the electric vector of light, in much the same way we see colour.     

Peptidoglycan recognition proteins: a novel family of four human innate immunity pattern recognition molecules.

The innate immune system recognizes microorganisms through a series of pattern recognition receptors that are highly conserved in evolution. Insects have a family of 12 peptidoglycan recognition proteins (PGRPs) that recognize peptidoglycan, a ubiquitous component of bacterial cell walls. We report cloning of three novel human PGRPs (PGRP-L, PGRP-Ialpha, and PGRP-Ibeta) that together with the previously cloned PGRP-S, define a new family of human pattern recognition molecules. PGRP-L, PGRP-Ialpha, and PGRP-Ibeta have 576, 341, and 373 amino acids coded by five, seven, and eight exons on chromosomes 19 and 1, and they all have two predicted transmembrane domains. All mammalian and insect PGRPs have at least three highly conserved C-terminal PGRP domains located either in the extracellular or in the cytoplasmic (or in both) portions of the molecules. PGRP-L is expressed in liver, PGRP-Ialpha and PGRP-Ibeta in esophagus (and to a lesser extent in tonsils and thymus), and PGRP-S in bone marrow (and to a lesser extent in neutrophils and fetal liver). All four human PGRPs bind peptidoglycan and Gram-positive bacteria. Thus, these PGRPs may play a role in recognition of bacteria in these organs.     

Improved learning capacity and discrimination performance of neural networks in pattern recognition of biosignals]

Pattern recognition was an important goal in the early work on artificial neural networks. Without arousing dramatic speculation, the paper describes, how a "natural" method of dealing with the configuration of the input layer can considerably improve learning behaviour and classification rate of a modified multi-layered perception with backpropagation of the error learning rule. Using this method, recognition of complex patterns in electrophysiological signals can be performed more accurately, without rules or complicated heuristic procedures. The proposed technique is demonstrated using recognition of the J-point in the ECG as an example.     

Information, discrimination and divergence in cytology. II. Total discrimination as a measure of performance

Discrimination is the expectation of log odds ratios. Performance in diagnostic cytology, as compared to the results of histopathology or to a peer-reviewed consensus, can be measured by the total discrimination, which is a well-defined measure of information in information theory and test theory. The total discrimination, as a measure of performance, was calculated for the Gynecologic Cytology Laboratory of the University of Minnesota for the years 1985 through 1987, based on 3,545 sets of single-slide Papanicolaou smears and colposcope-directed biopsies. Similar calculations were made for the performances of physicians and technicians on peer-reviewed "clear-cut" Papanicolaou smears, as reported in a study from the Centers for Disease Control (CDC). For fair comparison of the two different sets of observations, the cytologic categories and corresponding histologic states were merged into five categories and states. The cytologic performance of our laboratory, tested against the histologic diagnoses, and the performances of the physicians and technologists tested against peer-reviewed check samples by the CDC were 0.53, 0.45 and 1.17 decits, respectively. These values generally agree with the conclusions derived by more conventional methods used by the CDC. When sampling errors of cytology specimens are taken into account, the performance of our laboratory, measured by the total discrimination of the cytology-histology confusion matrix, was approximately equal to the performance of the group of technologists studied by the CDC, which was in turn significantly better than that of the group of physicians studied by the CDC. This study demonstrates the value of using the total discrimination for quantifying the performance of a cytology laboratory, a cytopathologist or a cytotechnologist, without the arbitrary means usually used to evaluate such performances.     

Fine discrimination in the recognition of individual species of phosphatidyl-myo-inositol mannosides from Mycobacterium tuberculosis by C-type lectin pattern recognition receptors

The Mycobacterium tuberculosis (M.tb) envelope is highly mannosylated with phosphatidyl-myo-inositol mannosides (PIMs), lipomannan, and mannose-capped lipoarabinomannan (ManLAM). Little is known regarding the interaction between specific PIM types and host cell C-type lectin pattern recognition receptors. The macrophage mannose receptor (MR) and dendritic cell-specific ICAM-3-grabbing nonintegrin on dendritic cells engage ManLAM mannose caps and regulate several host responses. In this study, we analyzed the association of purified PIM families (f, separated by carbohydrate number) and individual PIM species (further separated by fatty acid number) from M.tb H(37)R(v) with human monocyte-derived macrophages (MDMs) and lectin-expressing cell lines using an established bead model. Higher-order PIMs preferentially associated with the MR as demonstrated by their reduced association with MDMs upon MR blockade and increased binding to COS-1-MR. In contrast, the lower-order PIM(2)f associated poorly with MDMs and did not bind to COS-1-MR. Triacylated PIM species were recognized by MDM lectins better than tetra-acylated species and the degree of acylation influenced higher-order PIM association with the MR. Moreover, only higher-order PIMs that bind the MR showed a significant increase in phagosome-lysosome fusion upon MR blockade. In contrast with the MR, the PIM(2)f and lipomannan were recognized by DC-SIGN comparable to higher-order PIMs and ManLAM, and the association was independent of their degree of acylation. Thus, recognition of M.tb PIMs by host cell C-type lectins is dependent on both the nature of the terminal carbohydrates and degree of acylation. Subtle structural differences among the PIMs impact host cell recognition and response and are predicted to influence the intracellular fate of M.tb.     

Automated counting of phytoplankton by pattern recognition: a comparison with a manual counting method

Computer-based image analysis and pattern recognition methodswere used to construct a system able automatically to identify,count and measure selected groups of phytoplankton. An imageanalysis algorithm was employed to isolate and measure objectsfrom digitized images of a phytoplankton sample. The measurementsobtained were used to identify selected groups of phytoplanktonby a combination of artificial neural networks and simple rule-basedprocedures. The system was trained and tested using samplesof lake water covering an annual growth cycle from Lough Neaghin Northern Ireland. Total volume estimates were obtained forthe four major phytoplankton species, using both the automatedsystem and a manual counting method. Estimates of total cellvolume obtained from the automated system were within 10% ofthose derived by manual analysis of the same cells. The automatedsystem produced total cell volume estimates close to those obtainedfrom manual analysis of different aliquots of the same watersample. Variation between successive counts of the same watersample was higher with the automated system than with the manualcounting method. Limitations and possible improvements to thetechnology are discussed.     

The performance of ravens on simple discrimination tasks: a preliminary study

Recent studies suggest the existence of primate-like cognitive abilities in corvids. Although the learning abilities of corvids in comparison to other species have been investigated before, little is known on how corvids perform on simple discrimination tasks if tested in experimental settings comparable to those that have been used for studying complex cognitive abilities. In this study, we tested a captive group of 12 ravens (Corvus corax) on four discrimination problems and their reversals. In contrast to other studies investigating learning abilities, our ravens were not food deprived and participation in experiments was voluntary. This preliminary study showed that all ravens successfully solved feature and position discriminations and several of the ravens could solve new tasks in a few trials, making very few mistakes.     

New studies on odour discrimination in the frog's olfactory receptor cells. II. Mathematical analysis of electrophysiological responses

Revial et al. (1982) reported the experimental findings obtainedin cell units stimulated with two new sets of odorants. Thepresent paper deals with mathematical processing of these electrophysiologicaldata. The multidimensionality of the odour space was confirmed.Camphor, isoborneol and cineole appeared to represent a ‘camphorgroup’ markedly discriminated from other odorants. A‘terpenegroup’ including terpinene, dimethylstyrene, limoneneand cymene and related to menthane and menthene was observed.A series of 8 cycloketones was found to have a linear patternin the factorial planes and to be subdivided into three subsets.Cyclooctadecanone and cyclotetradecanone displayed correlationsand spatial relationships with musk ketone while cycloundecanone,cyclodecanone and especially cyclononanone were more relatedto the‘camphor group’. Separate processing of theunitary responses of 12 receptor cells recorded from a singlepreparation led to the building of a factorial space resemblingthat constructed with the full collection of data. The incidenceof odorant concentration on similarity evaluation is discussedon the basis of receptor responses to two different concentrationsof some of the odorants.     

Latency of recognition of geometrical figures with sides or corners masked to a different degree in humans

The effect of the degree of masking of sides or corners of geometrical figures on latencies of recognition of these figures has been studied in healthy subjects. It has been found that the latencies of recognition significantly and considerably increase if a greater part of a figure is masked. For all levels of masking, the latencies of recognition are longer for figures with partially masked corners rather than for those with partially masked sides. The findings are discussed in connection with previous data on better recognition of figures by means of corners than by sides, including possible neuronal mechanisms of the effects described.     

Aminoacyl-tRNAs from Physarum polycephalum: patterns of codon recognition.

Isoacceptors of Physarum polycephalum Ala-, Arg-, Glu-, Gln-, Gly-, Ile-, Leu-, Lys-, Ser-, Thr-, and Val-tRNAs were resolved by reverse-phase chromatography and isolated, and their codon recognition properties were determined in a ribosomal binding assay. Codon assignments were made to most isoacceptors, and they are summarized along with those determined in other studies from Escherichia coli, yeasts, wheat germ, hymenoptera, Xenopus, and mammals. The patterns of codon recognition by isoacceptors from P. polycephalum are more similar to those of animals than to those of plants or lower fungi.     

The correction of microtia with autogenous cartilage grafts: II. Atypical and complex deformities

Microtia encompasses a diverse variety of derformities whose correction must be considered individually. In part I, the classic form of microtia is described. In this article, an overview of complex microtic problems is presented and various techniques to facilitate their management are proposed.